A method for depositing III, IV semiconductor layers in the MOCVD method is described in DE 102007009145 A1, for example. This document describes a MOCVD reactor comprising a process chamber, which has a susceptor, in the case of which a plurality of substrates is arranged around a symmetry center in a substantially rotationally symmetrical arrangement. A gas inlet body, through which process gases are introduced into the process chamber through a plurality of gas inlet zones, which are arranged on top of one another, is located in the symmetry center. Process gasses, which differ from one another, flow into the process chamber through gas inlet zones of the gas inlet body in response to the growth process. The process gases are organometallic compounds, which contain an element from the III main group, and hydrides, for example NH3. The process gasses flow from the radially inner gas inlet body to a gas outlet ring, which surrounds the process chamber and through which the process gas leaves the process chamber again.
DE 102012102661 describes a method, by means of which the coatings, which are not only deposited on the substrates in response to the layer growth, but which are also deposited on the walls of the process chamber, can be removed again. An etching gas, for example Cl2, is introduced into the process chamber for this purpose. Parasitic coatings on the walls of the susceptor, on the process chamber ceiling and other process chamber walls are removed by means of this etching gas. The etching gas is introduced into the process chamber together with N2. This takes place through the gas inlet zones of the gas inlet body, through which the corresponding process gases are introduced into the process chamber in response to the layer growth. To clean different zones of the process chamber in consecutive partial steps, the cleaning gases are introduced into the process chamber at different locations under hydrodynamic conditions, which differ from one another. The cleaning steps, which differ from one another, are carried out in response to total gas pressures, which differ from one another, or in response to average flow speeds, respectively. The partial gas pressures of the cleaning gas, thus in particular Cl2, can vary as well. By introducing Cl2, GaN but also elemental Ga can be removed from the walls of the process chamber.
During the layer growth, the growth conditions are often set in such a manner that the deposited semiconductor layers do not only contain GaN, but also C as dopant. In any event, C is contained in the organometallic compounds, which form a gaseous source material. For example, trimethyl gallium disintegrates into gallium and a methyl residue, wherein the methyl residue can also disintegrate again. The carbon created thereby or the hydrocarbon-containing compounds created thereby, respectively, can adhere to the surface of the process chamber walls.
It is observed that a soot-like film remains on the walls of the process chamber after the cleaning step, as his described in DE 102007009145 A1.
US 2003/0045098 A1 describes the cleaning of surfaces of substrates with the help of etching gases. O2, N2, H2O, NH3, CF4, C2F6, CHF3, C3H2F6, C2H4F2 or CH3F are proposed as etching gases. A photoresist mask is to also be capable of being removed by means of these etching gases. Nitrogen-containing and oxygen-containing gases are to be introduced into the process chamber simultaneously in this document.
WO 2010/129183 proposes the use of ammonia as cleaning gas at temperatures of above 1,000° C., so as to remove GaCl3 from a process chamber.
US 2013/0005118 A1 describes a CVD process, in the case of which N2/H2 or NH3 as well as HCl are added to gaseous source materials, which contain elements of the III main group.
It is known from WO 2010/129289 to heat up a process chamber in the presence of ammonia, so as to remove GaCl3 deposited on the process chamber walls.